A portion of the cost of products incorporating welded seams joining metal panels is attributed to the material cost of the metal panels that are welded, as well as the length of time required to perform the welding. Enclosures, such as freezers and ovens, are typically manufactured using relatively thick stainless-steel panels (e.g., 16-gauge) welded in the field using tungsten-inert-gas (TIG) welding. The thick metal contributes to the cost of the finished product, as does the TIG welding, which is relatively slow when compared to other welding techniques.
An improvement to the welding of enclosures is the use of metal-inert-gas (MIG) welding instead of TIG welding, which delivers a speed increase from, for example, 2 inches per minute (TIG) to 12 inches per minute (MIG). However, MIG welding is difficult to perform in the field (as opposed to in the manufacturing shop) because of the inert gas requirements (e.g., wind disrupts welding by dispersing the inert gas). Additionally, manual MIG welding requires relatively thick metal so as to avoid warping due to thermal effects during welding.
Other methods for improving the speed and overall efficiency of welding panels include automated seam-tracking systems. Representative seam tracking systems include systems having laser tracking using optical transmission and detection to visualize a seam and guiding a welding apparatus along the detected seam. Laser tracking systems require a large welding apparatus that includes not only a welding head, but also a complex optical system and related processing equipment for utilizing laser tracking. Because of its large size, laser tracking is typically only possible in a manufacturing shop environment and is not portable to the field.
Another method for seam tracking includes the use of a stylus probe for tracking a seam, where a stylus is set in a seam and guides the welding apparatus based on physical contact between the stylus and the seam. Stylus probe tracking systems have been shown to weld seams at approximately 30 inches per minute, an improvement over manual welding. However, the use of a stylus probe tracking system requires tracks to be mounted parallel to the weld seam and a typical unit weighs in excess of 50 lbs. Similar to the laser optical system, the stylus probe system is bulky and requires track set up time for each weld.
Hygiene-sensitive customers, particularly those in the food industry, often require an enclosure with fully-welded seams. Fully-welded seams are more time-consuming to fabricate compared to spaced apart or periodic welds and also create thermal-management issues that reduce the speed at which a weld can be made due to the possibility of warping from localized heating. Additionally, insulated panels used for forming insulated enclosures are particularly susceptible to warping and damage from localized heating during welding.
A method for fabricating fully-welded enclosures made from relatively thin metal material that can be welded at a high rate of speed would be beneficial for the manufacturing of welded enclosures. By using thinner material, material costs would be saved, and by welding more quickly, labor costs would be saved and production could be increased. However, heat-management issues and a lack of a field-deployable automated seam-tracking welder have thus far precluded such a method.